The invention relates to methods of separating impurities or contaminants from liquids such as water by means of a two-stage process.
In conventional processes and apparatus of this type, a pair of separate treatment tanks are respectively charged with contamination-removing substances, and the liquid to be treated is then propelled in tandem through the first and second tanks to be purified. Typically, the first tank is operated in selective closed-loop fashion, whereby when the associated contamination-removing substance (which may be a filtration material, adsorbing material or ion exchanger) becomes spent, a transport fluid is introduced into the top of the first tank to propel the spent substance out of the treatment tank and into a rinsing or regeneration tank for renewal, i.e., for separation of the contaminants obtained from the treated liquid. After such renewal, the regenerated substance is recirculated back into the first tank as a fresh charge.
Additonally, the separate second tank in such installations is generally operated in an open-loop fashion, whereby the contaminant-removing substance therein (e.g., a final filtration material such as activated charcoal) is renewed in situ by the passage of rinsing water therethrough.
It has been found that such two-stage decontamination facilities are space-consuming and expensive to operate.